Vertical synchronization circuit for television receivers



CHRONIZATION CIRCUIT FOR TELEVISION RECEIVERS 5 Sheets-Sheet l FiledSept. 28, 1950 Kurt fzsZeL'fz, BY

ATTORNEY March 16, 1954 K. ENSLEIN VERTICAL SYNCHRCNIZATICN CIRCUIT FORTELEVISION RECEIVERS 5 Sheets-Sheet 2 Filed Sept. 28, 1950 .K wm, N a,QW mw Il Il l E llllllllllll Il 1 Ww la I w I k f r J L v QJIK H Hmm, wmw .u M 1 M I WVM um .www L.. mw |I|\O 00# d5 wlw CN mw QM mw .NG .www Wl0.5m MC. I l Il I Q@ \N ATTORNEY March 16, 1954 K. ENSLEIN 2,672,510

VERTICAL sYNCHRoNIzATIoN CIRCUIT FOR TELEVISION RECEIVERS Filed Sept.28, 1950 5 Sheets-Sheet 3 BYJXWM/ ATTORNEY March 16, 1954 K. ENSLEIN2,672,510

VERTICAL SYNCHRONIZATION CIRCUIT FOR TELEVISION RECEIVERS Filed Sept.28, 1950 5 Sheets-Sheet 4 N INVENTOR.

l C Kaff 'nslel'lz BY JKM ATTORNEY March 16, l954 K. ENsLElN 2,672,510

VERTICAL sYNcHRoNIzATIoN CIRCUIT FOR TELEVISION REcEIvERs Filed Sept.28, 1950 5 Sheets-Sheet 5 y INVENTOR. NAB Kart slen BY d X ATTORNEYPatented Mar. 16, 1954 ONIZATION CIRCUIT VERTICAL SYN CHR FOR- TELEVISKurt Enslein,

I-N RECEIVERS Rochester, N. Y., assignor to Stromberg-Carlson Company, acorporation of New York Application September 28, 1950, Serial No.187,207 2s claims. (c1. iis-69.5)

The present invention relates to television receivers, and moreparticularly, to synchroniza-i tion circuits for the vertical scanninggenerator of a television receiver.

In many instances, itis desirable to provide a pulsesynchronizationcircuit for a low frequency oscillator. Such an instancearises in the case of television receivers wherein it is necessary tosynchronize both a relatively high frequency horizontal scanninggenerator and a low frequency vertical scanning .generator toreconstruct the transmitted image. Certain arrangements heretofore.proposed have employed arrangements for direct synchronization of thevertical scanning generator in which the .composite synchronizing signalis simply integrated and applied to the vertical scanning generator.This arrangement is quite sensitive to noise interference since noattempt is made to remove the noise present in the original signal.Also, such arrangements are unsatisfactory in that a large noise pulsemay cause the preceding ampliiiers to block for a long enough periodthat the next succeeding pulse is not produced, and hence consistentstable triggering of the Vertical scanning generator is-not obtained.

While .certain other arrangements heretofore proposed have .employed aresonant circuit to discriminate against noise voltages by means of theso-called Iiywheel effect of the oscillatory circuit, these arrangements.employ a resonant circuit of substantially the same frequency as thesynchronizing pulses and are relatively unsatisfactory for low frequencywork suchas is required in the vertical synchronization circuit of atelevision receiver both from the standpoint of cost and eniciency of.operation.

In conventional television receivers it is also common practice toemploy an automatic frequency control circuit, commonly called an AFCcircuit, for controlling the frequency of the horizontal scanninggenerator to stabilize this generator and to reduce the susceptibilityof the generator to respond to noise pulses. Such an AFC circuit may,for example, comprise a phase and frequency sensitive circuit having arelatively long time constant so that it is relatively insensitive toshort time transients. However, no such AFC circuit is conventionallyemployed in connection with the vertical sweep generator inasmuch as anAFC circuit for both horizontal and vertical generators is prohibitivefrom the cost standpoint.

.-Accordingly, it is a primary object of the present invention toprovide a newand --improved vertical synchronization circuit for atelevision receiver. i I

It is another object of the present invention to provide a new andimproved verticalA synchronization circuit for a television receiver inwhich substantial discrimination against noise voltages and otherextraneous impulses is provided;

It is a further object of the present invention to provide a new andimproved vertical synchronization circuit for a television receiverwhich is extremely stable and which operates satisfactorily regardless`of variations in the supply voltages and the constants of the circuitcomponents. l

Still another object of the present invention resides in the provisionof a new and improved vertical synchronization circuit for a televisionreceiver which is extremely simple-in arrangement and is of low cost andwherein a substantial discrimination against noise impulses is achieved.

It is a further object of the present invention to provide a new andimproved vertical synchronization circuit for a television receiverwhich is stabilized by means of an automatic frequency controlledhorizontal scanning generator of the receiver.

It is a still further object of the present invention to provide a newand improved vertical synchronization circuit for a television receiverin which an automaticfrequency controlled horizontal scanning generatorof the receiver is employed as a standard to control at least in partthe operation of the vertical synchronization circuit.

The invention, both as to its organization and method ofoperation,'together with furtherobjects and advantages thereof, willbest-be un derstood by reference to the following specification taken inconnection with the accompanying drawings, in which: l y A.

Fig. 1 is a block diagram of a television receiver employing thevertical synchronization circuit of the present invention; A

Fig. 2 is a detailed schematic diagram of one form of the verticalsynchronization circuit of the television receiver shown in Fig. 1; 1

Fig. 3 is an alternative embodiment of the present improved verticalsynchronization circuit whichV may be employed in the televisionreceiver of Fig. 1; and

Figs. Lict-fig show a series of timing diagrams illustrating the waveforms which occur in the circuits of Figs. 2 and 3. Y

Referring now to the drawingsv and more particularly to Fig. 1 thereof,the system there illustrated comprises a television receiver of thesuperheterodyne type including an antenna system I0, connected to aradio frequency amplifier Il, to which are connected in cascade, in theorder named, a first detector and oscillator I2, an intermediatefrequency amplifier I3, a second detector I4, a video frequency amplierI and an image reproducing cathode ray tube I6. The output of thedetector I4 is coupled through a synchronizing pulse clipper I1, theoutput of which is coupled through an AFC circuit I8 and a horizontalsweep generator I9 to the horizontal deiiecting windings 2li whichsurround the neck of the cathode ray tube I6. The ouput of thesynchronizing pulse clipper II is also connected to the verticalsynchronizing circuity 2l of the present invention, which in oneembodiment is also controlled by the horizontal scanning generator I9over the conductor 25, the ouput of the circuit 2I being connectedthrough a vertical sweep generator 22 to the vertical deflection coils23 which also surround the cathode ray tube I6. The stages or units IDto I9, inclusive, and 22 may all be of conventional well knownconstruction so that a detailed illustration and description thereof isdeemed unnecessary herein.

Referring briefly, however, to the general mode of operation of thesystem described above, television signals intercepted by the antennacircuit IIIare selected and amplified in the radio frequency amplifierII and transmitted to the first detector and oscillator I2. where theyare converted into intermediate frequency signals which, in turn, areselectively amplified in the intermediate frequency ampliiier I3 anddelivered to the second detector I4. The modulation components of thesignal are detected by the second detector I4 and the video frequencysignals are supplied to the video frequency amplifier i5 where they arefurther amplified and from which they are supplied in theusual manner tothe brillance control electrode of the image reproducing device i5. Thecomposite television signal is supplied to the synchronizing pulseclipper I'I which separates the composite synchronizing signal from thevideo signals and supplies the composite synchronizing signal to the AFCcircuit I8 and the vertical synchronization circuit 2i. Scanning wavesare generated in the horizontal and vertical sweep generators I9 and 22,which are controlled by synchronizing voltages supplied thereto from theunits I8 and 2i, and are applied to the scanning coils 20 and 23 toproduce electromagnetic scanning fields, thereby to deflect the scanningray in two directions perpendicular to each other so as to trace arectilinear scanning pattern on the screen and to reconstruct thetransmitted image.

Referring now more particularly to the portions of the system of Fig. lembodying the present invention there is shown in Fig. 2 the improvedvertical synchronization circuit of the present invention which`includes a narrow band amplifier 30, an electronic switching circuit 3l,and anl integration network and ouput amplifier .32. The compositesynchronizing signal is supplied from the synchronizing pulse clipper ilthrough the coupling condenser 35 to the control electrode of a pentodetype amplifier tube 36. The control electrode of the tube 36 is biasedby means-ofl a conventionalself biasing network 31 in the cathodethereof, and a parallel resonant amplified by the tube .circuitvcon'iprising the inductance Stand the. 75

eondensers 39 and 40 is connected between the control electrode of thetube 36 and ground.

Signals developed at the anode of the tube 36 are coupled through thecondenser 45 to the electronic switching circuit 3|. The switchingcircuit 3I comprises a pair of pentode type tubes 5I and 52, thesynchronizing signal supplied from the condenser 45 being coupled to thesuppressor grid of the tube 5I. The anode of each of the tubes 5I and 52is cross-connected to the control electrode of the opposite devicethrough one of the resistor-capacitor networks, 53 and 54. The controlelectrode of the device 5I is also connected to ground through theresistor 55 and is further connected through the resistor 56 to a sourceof negative bias potential. Likewise, the control grid of the tube 52 isconnected through the resistor 5l to ground and through the resistor 58to the negative source of bias, potential. Control pulses from thehorizontal sweep generator I9 are supplied through the input terminalSi) and the coupling condenser 6i to the suppressor grid of the tube 52.

A reconstructed synchronizing voltage which appears at the control gridof the tube 52 is directly coupled to the control grid of a driver tube55, included in fied synchronizing voltage appearing at the anode of thetube S5 is coupled through an integrating network including theresistors 66 and l2 and the condensers 5l and 'I3 and through thecoupling condenser 68 to the control grid of a cathode follower outputtube 19. An output voltage suitable for driving the vertical scanninggenerator 22 yis derived from the cathode of the tube I0 and appears atthe output terminal 'i I.

Considering now the operation of the abovedescribed verticalsynchronization circuit, the resonant circuit 3B, 39 and 4t is adjustedby variation of the condenser 40 so that the resonant frequency thereofis substantially higher than the frequency of the horizontalsynchronizing pulses supplied from the synchronizing pulse clipper I'I.Preferably the frequency of the tuned circuit 38, 39 and 46 is Withinthe range of 108 to kilocycles. Also, the band width of the resonantcircuit is preferably quite narrow so as to obtain maximum rejection ofnoise impulses and other extraneous voltages which may be supplied tothe vertical synchronization circuit 2l from the synchronizing pulseclipper Il. The composite television synchronizing signal which is cfnegative polarity and which includes horizontal and verticalsynchronizing pulses, is coupled to the resonant circuit 33, 39 and llthrough the condenser 35 and these pulses are injected into the resonantcircuit so as to shock excite the resonant circuit into oscillation atits natural resonant frequency, There is thus produced across theresonant circuit a series of damped sinusoidal wave trains which startcoincident with the beginning of each of the synchronizing pulses andwhich gradually decay to minimum amplitude just prior to the nextsucceeding synchronizing pulse.

The damped sinusoidal wave trains produced across the resonant'circuit38, 39, and 4G are 36, are inverted in polarity in this tube, and aresupplied through the coupling condenser 45 to the suppressor grid or thetube 5I in the electronic switching circuit 3i. The switching circuit 3iis of the type commonly referred to as an Eccles-Jordan trigger circuitin which the tubes are alternately'switched from a fully conductive to anonconductive stateginrethe output amplifier 32. Amplinizing thevertical sweep generator 22 of the bistable lspense totriggeringpulses-applied to the suppresser grids of each tube. Thus,when thel tube I is conducting, the voltage dividing network includingthe resistors 53a, 5l and 58, which is connected between the anode ofthe tube iii and the negative supply potential, is so chosen that thetube 52 will be driven beyond cutoff and hence will not be conductive.However, when a negative pulse, for yexample-the initial portion of oneof the damped sinusoidal wave trains produced in amplified form at theanode of thetube 3B, is supplied to the suppressor grid of the tube 5I,this tube is rendered nonconductive and the circuit abruptly switchessothat the tube 52 becomes fully conductive and the tube 5I is cut off.Under these conditions it is necessary to turn o the tube 52 bysupplying to they suppressor grid thereof a negative pulse in order toswitch the circuit back to its original condition. To accomplish this,negative control pulses which are derived from the horizontal scanninggenerator of the television receiver are impressed upon the suppressorgrid of the tube 52 over a path which includes the conductor 25, thecondenser 6I and the input terminal 60.

In considering the operation of the abovedescribed Eccles-Jordan triggercircuit, it will be understood that the circuit is insensitive to pulsesof positive polarity so that only negative pulses are operative t-otrigger the circuit from one conductive state to the other. It is thusseen from the foregoing description that the switching circuit 3| iskeyed by means of the damped sinusoidal wave trains to a rst conductiveposition and is keyed to the opposite conductive position in response toeach of the control pulses supplied to the tube 52 from the horizontalscanning generator I9. With this arrangement, a composite horizontal andvertical synchronizing pulse wave is reconstructed at the control gridof the tubey 52 which is coupledthrough the driver tube 65 to theintegration components, including the resistor 56 and the condenser S1,of the network 32. The integration network 32 lintegrates thereconstructed synchronizing signal formed in the switching circuit 50 toprovide triggering pulses which have a recurrence rate equal to that ofthe original vertical synchronizing pulses. These triggering pulses aresuitable for controlling the frequency of a conventional verticalsweep'generator, such as the generator 22. More specilically, thetriggering pulses thus produced in the integration circuit 32 are fed tothe cathode follower output tube 'It so that there is produced at thecathode of the tube l0 positive triggering pulses which are suitable fordirectly synchrosweep generator 22. In this connection it will beunderstood that the vertical television receiver may be of any suitabletype which is adapted to be synchronized by means of pulses which occurat the frame frequency. Thus, the vertical scanning generator 22 mayinclude a conventional blocking oscillator which is directlysynchronized by the pulses produced at the cathode of the tube 10, as'

will be readily understood by those skilled in the art. i

In order more clearly to visualize the operation of the above-describedvertical synchronizing circuit, reference is now made to Figs. 4(a)through I(e) inclusive, wherein certain wave forms which occur atvarious points in the circuit of Eig. 2 are illustrated. Referring moreparticulaily to Fig. Ma), this gure illustrates thev compositetelevision synchronizing` signal which is supplied Y switched to the`which are in turn followed by the horizontal synchronizing pulses 8D.

In Fig. 4(b) there is illustrated the succession of damped simusoidalwave trains 85, which are produced across the resonant circuit Si?, 39and 40, in response to the'pulse portions of the composite signal ofFig. 4(a). It will be seen from an inspection of Fig. Mb) that theleading edge 8G of the damped wave train coincides with the negativegoing portion of the horizontal equalizing and vertical pulses shiown inFig. 4m). Thus, the leading edge 85 of the nrst pulse wavetraincoincides with the leading edge bi of the iirst horizontalsynchronizing pulse Bil. Likewise, the leading edge St of the dampedwave train 39 coincides withv the leading edge S9 of the firstequalizing pulse 9|. Also, the leading edge 52 of the damped wave trainS3 coincides with the negative going vedge 913 'of the verticalsynchronizing pulse tia'. In an entirely similar manner, the leadingedges ofthe remaining damped wave trains coincide exactly with thenegative going edges of succeeding synchronizingV pulses.

As explained above,`the clamped wave trains illustrated in Fig. 4(1))are ampliied by the tube 36 (Fig. 2) and dierentiated in the circuitincluding the condenser 65 and resistor 66 so as to provide the waveform shown in Fig. 4(0). It wiil be noted that the diterentiated waveform of Fig. file) comprises a series of positive pulses I Ill which areimmediately followed by the negative pulses mi. The pulses lill! aresubstantially coincident with the leading edge of each of the dampedwave trains 85 so that there is produced, asa result of diierentiation,the negative pulses I9! which occur slightly after the start of eachdamped wave train.v

The control pulses which are derived from the horizontal scanninggenerator E9 are illustrated inv Fig. r(d). Referring to this gure,these control pulses are the pulses I It, which occur substantiallycoincident with the horizontal synchronizing pulses Sil and are producedduring y the retrace, or flyback interval of the horizontal scanninggenerator I9. As indicated above-the pulses `Ilo may be directlysupplied from the secondary of the horizontal sweep transformer 2t asshown in Fig. l. By comparingFigs. 4(0) and 4(01) it will be seen thatthe pulses I I Il occur sE-.ightly before thepulses I GI, so that theswitching circuit 3i may be keyed to one position by the control pulsesIIE and may thereafter be kopposite position by means of following pulselili, such. that the wave form shown in Fig. 40e) is reconstructed atthe control grid of the tube 52.

' Considering Figs. 4(0), Hd) and. @(e) together, it will be seen thatthe rst pulse llt keys the switching circuit 3I to a given condition soas to produce the leading edge I Zii of the first pulse shown in Thenext succeeding pulse p lol from the ammieaas keys the switching cirduce'the trailing edge I2 I i In .trains on an amplitude @secano ner, thecontrol pulse produces the leading edge |22 and the following negativepulse |02 produces the trailing edge |23. During. the equalizing pulseinterval, the negative control pulse ||2 produces the leading edge |24and the first succeeding negative pulse |03 produces the trailing edge|25. The intermediate negative pulse |04 is inoperative to key theswitching circuit 3| due to the fact that the circuit 3| has alreadybeen keyed by the previous pulse |03. Accordingly, the equalizing pulses8| are not reconstructed in the wave form of Fig. Me). During thevertical pulse period the control pulse I3 produces the leading edge |26(Fig. Mel) and the next succeeding pulse produces the trailing edge |21of the reconstructed pulse shown in Fig. 4(6). The remaining verticalpulses and horizontal pulses are reconstructed in the switching circuit3| in an entirely similar manner.

The pulses of the reconstructed wave form shown in Fig. 4(e), namely thepulses |30, which correspond to the original horizontal synchronizingpulses and the pulses 13| which are substantially similar to theoriginal vertical synchronizing pulses, are integrated in theintegration circuit 32 so as to provide the wave form shown in Fig.4(1). Referring to this figure, during the interval of the short pulses|39, the integration network produces an output wave |34 of minimumamplitude. However, during the relatively long pulses |3|, a positivetriggering pulse |35 of larger amplitude is produced which substantiallyspans and coincides with the original vertical synchronizing interval,or in other words, the period occupied by the pulses 82 (Fig. 4(01) Thetriggering pulse |35 is predominately positive and may be used totrigger the vertical scanning generator 22 in a manner which will beunderstood by those skilled in the art.

From the foregoing description, it will be understood that the presentinvention is substantially different from the so-called ywheel type ofsynchronization arrangement in which the synchronizing pulses areinjected into a resonant circuit having a natural resonant frequencyequal to that of the desired synchronizing pulses. In the improvedvertical synchronization circuit described above, the frequency of theresonant circuit 33, ly higher than the relatively high frequency ofoccurrence of the horizontal synchronizing pulses, although a relativelylow frequency vertical triggering pulse is eventually derived from thesinusoidal wave train produced across the resonant circuit. Also, theresonant circuit is suiiiciently damped so that the amplitude of theoscillations produced thereacross in response to each high frequencypulse can decay by a substantial amount before the next pulse. With thisarrangement, the vertical synchronizing pulses, which occur during thevertical synchronizing interval and are of substantially differentenergy content than the horizontal synchronizing pulses, can influencethe wave form of the damped wave basis Aso that subsequent integrationproduces a triggering pulse of relatively low frequency which issuitable for triggering a vertical scanning generator as describedabove. If the frequency of the resonant circuit is made too low, or theresonant circuit is undamped, a continuous sine wave of substantiallyconstant amplitude results thus preventing vdiscrimination on anamplitude :,basisbetween A the horizontal and vertical synchronizingintervals.

39 and 40 is substantialwith those employed in control electrode of theamplifier tube .ever,the anode circuit of -`tos 1.ippl y anwoutputwaveyto the terminal |40 A further important feature of the present; in-

.vention resides Ain the above-described utilization of control pulsesfrom the horizontal scanning generator I9 to at least partially controlthe keying of the switching circuit 3|. According to the presentinvention, the horizontal scanning generator I9 is controlled by meansof the AFC circuit I8, which may comprise any suitable phase andfrequency sensitive control circuit which is substantially independentof noise impulses and Aother undesired disturbances so that thehorizontal generator |3 is extremely stable in freo uency andinsensitive to noise. The AFC circuit |8 may comprise, for example, aphase comparison circuit in which a relatively long time constant isemployed to derive a substantially unidirectional voltage which isrelatively independent of noise impulses and other disturbances. In thevertical synchronization circuit of Fig. 2, the stable horizontalgenerator I3 acts as a standard, or reference control voltage for thevertical synchronization circuit. With this arrangement a stable noisefree vertical scanning wave is produced without employing a separate AFCcircuit for vertical synchronization.

Also, the use of the switching circuit 3| provides additionaldiscrimination against noise due to the fact that the only informationwhich is necessary to key the Eccles-Jordan trigger circuit is timeinformation. Furthermore, in one direction, i. e, the directioncontrolled by the control pulses from the horizontal scanning generator,this switching circuit is additionally staoilized by the automaticfrequency control circuit associated with the horizontal generator.Accordingly, a substantially noise-free vertical triggering pulse |35(Fig. 4f) is provided and the vertical synchronization system issubstantially independent of supply voltage variations and variations inthe constants of circuit components. In addition, the use of theresonant circuit 30, 39 and 00 in the input circuit of the amplifier 35provides additional noise discrimination due to the narrow pass band ofthis circuit, as a result of which noise components falling outside thepass band of the resonant circuit are rejected and the oscillationsproduced in the resonant circuit are substantially noise-free. In thisconnection, it is repeated that the pass band of the resonant circuitand its associated amplifier 36 is made quite narrow in order to obtainmaximum noise discrimination. Moreover, the vertical trigger pulse |35,which has a fundamental frequency of sixty cycles, is produced uponintegrating the reconstructed synchronizing signal shown in Fig. Mc)without interfering with the noise reducing action of the narrow bandcircuit.

To provide a simplified vertical synchronization arrangement, whereinsubstantial noise discrimination is achieved and reliablesynchronization is provided with a minimum number of circuit components,the alternative embodiment of the present invention shown in Fig. 3 maybe employed. In this modified arrangement, certain Acomponents of thesystem of Fig. 3 are identical the circuit of Fig. .2, and accordinglythe same reference numerals have been used to identify the samecomponents of the two circuits. In the circuit of Fig. 3 the compositetelevision synchronizing signal is again supplied through the couplingcondenser 35 to the resonant circuit 38, 39 and 40, and to the 30.Howthetube 35 is employed ama-mo which may bel utilizedl receiver. Forexam-ple, wave trains produced at 36 may be employed tofeiectsynchronization oi the horizontal scanning generator I9, in which casethe AFC circuit Hiy is not required. Accordingly, the verticalsynchronization signal is derived from the screen electrodes |,4.| ofthe tube 36, the screen electrode being connected to the. B+ supplythrough the load resistor |42. The integration network is directlyconnected to the screen electrode` HHy and comprises the resistorsv E6and 12 and the condensers 61 and 'I3 in a manner similar to theintegrationv network shown in Fig. 2. The integrated verticalsynchronization pulse produced in the integration network 65 and 6`| issupplied to the output, terminal |45 from which it maybe connected inany suitable manner, as through the cathode follower '|0 (Fig- 2)y tothe vertical scanning generator 22 to eiect synchronization thereof bytriggering of the generator.

In considering the operation of the simplified circuit Iof Fig. 3 itwill be seen that the composite wave form shown in Fig. 401i)y againoperates to produce a series of damped wavev trains across the resonantcircuit 30, 39 and 4,0 as shown in Fig. 4(0) and discussed in`connection therewith, The damped sinusoidal wave trains. 85 areamplified in the tube 36 and are inverted in polarity so as to appear asdamped wave trains of the opposite polarity at the screen electrodevlill.V In the circuit of Fig. 3, however, the composite synchronizingsignal is not reconstructed` in the manner shown in Fig. 4(e) butinstead the wave trains 85 are directly integratedr toproduce theintegrated wave shown.- in Fig. 4(9). Referring toA this figure, it willbe seen that during each interval spanned by the horizontalpulses 50ithere is produced an output wave of minimum amplitude, as shown at |50.During the equalizing pulse interval the averagev value of the wavetrains 89 decreases soas to produce the negative going wave portion |5|.However, during the vertical synchronizing interval,` i. e., during; theinterval spanned by the pulses 8-2 (Fig. 4a), the average value of thewave. train 93 is predominantly positive so as to producethe relativelysteep-sided pulse |52. The triggering pulse |52v may be supplieddirectly from the integration circuit BS and 51 to the vertical.scanning genera-- tor. In this connection it will, be noted that: thevertical triggering pulse |52 (Fig. 4d) is of larger amplitude than thecorresponding triggering pulse |35 which is provided, in theverticalsynchronization circuit of Fig. 2. This is due to the fact thatthe reconstructed wave: form shown in Fig. 4(e) has a smalleraverage'value during the vertical synchronizing interval as.y will beevident from a comparison of the pulsesk |a3,|- and the pulses 82 (Fig.4a).

While there is illustratedain Fig'. 2 a switching circuit employingpentode type tubes 5ta-nd 52, it will be evident thaty various otherarrangements may be employed. For example, triode type switching tubesmay be employed.l together with suitable clipping circuitsv forpreventing triggering of each tube by pulses, other than pulses of agiven polarity; Likewise, other types of narrow band ampliiiers mayloe-employed to provide discrimination: against. noise: impulses andother extraneousvoltages.

By way of illustration and not.l in4 any sense as a limitation to thephysicalvalues given),` the following circuit constantsihaye been.yfound. sui

i-n another portion of the the damped sinusoidal;` the. anodeof. thetube- 10 able in a. vertical synchronization circuit constructed asshown in Fig. 2 and wherein the tube 35 was a commercial type 6CB6, thetubes 5|` and 52 commercial typev 6AS'6s, *andy the tubes 55 and 10 adual triode commercial type- 12AU7. Other circuit constants follow:

Condenser 35 mmf-- 39 Condenser 39 mmf 820 Condenser 40 mmf 50 Condenser45 mmf 10 Condenser 5| mmf-- 22 Condenser -67 mmf-- 680 Condenser 50 mfd.0lv Condenser 13 mmf-- 2,200 Resistor 45 ohms 47,000 Resistor 53 ohms68,000 Resistor 54 ohms 68,000 Resistor 55 ohms-; 10,000A Resistor 55ohms 51,000 Resistor 51 ohms-- 10,000 Resistor 58 ohms 51,000 Resistor62 ohms 47,000 Resistor 66 ohms-- 47,000 Resistor 72 ohms 22,000Inductance 38 mh 1.9

While there have been described what are at present considered to be thepreferred embodiments of the invention it will be understood thatvarious modications may be made therein which are within the true spiritand scope of the in- Vention as dened in the appended claims.

What isv claimed as new and desired to be secured by Letters Patent ofthe United States 1. In a television receiver, the combination of, asweep signal generator, means for receiving and detecting synchronizingpulses, means responsive to each detected pulse for producing a dampedsinusoidal wave train, means for integrating said damped wave trains tovproduce triggering pulses in time coincidencewith said detected pulses,and means for applying said triggering pulses to said generator tocontrol the operation of said generator.

2. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals including meansfor providing horizontal and vertical synchronizing pulses, means forderiving from said source a damped sinusoidal wave train in responseto:each of said vertical and horizontal synchronizing pulses, means forvintegrating said damped wave trains to provide triggering pulsessubstantially coincident with said vertical synchronizing pulses, andmeans for controlling said vertical scanning generator in accordancewith said trig.- gering pulses.`

3. In a television receiver, the combination of, a verticalscanning-generator, ar source-of television synchronizing signalsincluding horizontal and vertical synchronizing pulses, means includinga narrow bandresonant circuit tunedv to a frequency higher than saidhorizontal synchronizing pulses for deriving` from Asaid source a dampedsinusoidal' wave train in, response to each of' said pulses, means forproducing from said damped wavetrains triggering pulses in time.coincidence with said vertical" synchronizing pulses, and means forcontrolling said vertical scanning generator in. accordance with saidtriggering pulses. f y

4. In a television'receiver, the'4 combination, of, a. vertical scanninggenerator, a source. 'of'television. synchronizinge signals includinghorizontal and vertical synchronizing pulses; means for Il deriving fromsaid source a damped sinusoidal wave train in response-to each of saidpulses, means including an integration network for deriving from saiddamped wave trains triggering pulses in time coincidence with saidvertical synchronizing pulses, and means for controlling said verticalscanning generator in accordance with said triggering pulses.

'5. In a television receiver, a combination of, alvertical scanninggenerator, a source of television synchronizing signals includinghorizontal and vertical synchronizing pulses, means for deriving fromsaid source a sinusoidal Wave train having amplitude variationscorresponding to said vertical and horizontal synchronizing pulses,means for integrating said sinusoidal Wave train to provide triggeringpulses having a recurrence rate equal to that of said verticalsynchronizing pulses, and means for controlling said vertical scanninggenerator in accordance with said triggering pulses.

6. In a television receiver, the combination of, a vertical scanninggenerator, a'source of television synchronizing signals includinghorizontal and vertical synchronizing pulses, an amplifier coupled tosaid source and tuned to a frequency substantially higher than thefrequencyof said horizontal synchronizing pulses, means for integratingthe output of said amplifier to obtain triggering pulses, and means forsynchronizing i said vvertical scanning generator gering pulses.

4 7. In a television receiver, the combination of, a vertical scanninggenerator, asource oftelewith said trigvision synchronizing signalsincluding horizontal and vertical synchronizing pulses, means includingan amplifier coupled to said source for deriving a damped sinusoidalwave train in response to each of said horizontal and vertical pulses,means for integrating said damped wave trains over a period long ascompared to the time between said horizontal synchronizing pulses andmuch shorter than the period of said vertical synchronizing pulses, andmeans for synchronizing said vertical scanning generator with saidintegrated damped wave trains.

8. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includinghorizontal and vertical synchronizing pulses, means for deriving adamped sinusoidal wave train having a frequency substantially higherthan said hori- 'zontal synchronizing pulses in response to each of saidhorizontal and vertical synchronizing pulses, means for integrating saiddamped wave trains to provide triggering pulses at the recurrence rateof said vertical synchronizing pulses, and means for controlling saidvertical scanning generator in accordance with said triggering pulses.

9. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includinghorizontal and vertical synchronizing pulses, a resonant circuit, meansfor injecting television synchronizing signals from said source intosaid resonant circuit to produce a sinusoidal wave train thereacrosshaving amplitude variations corresponding to said vertical andhorizontal synchronizing pulses, means for integrating said sinusoidalwave train to provide triggering pulses having a recurrence rate equalto that of said vertical synchronizing pulses, and means for controllingsaid vertical scanning generator in accordance with said triggeringpulses.

10. In a television receiver, the combination of,v

a vertical scanning generator, a source of television synchronizingsignals including horizontal and vertical synchronizing pulses, aresonant circuit tuned to a frequency substantially above the frequencyof said horizontal synchronizing pulses, means for coupling saidtelevision synchronizing signals into said resonant circuit to producedamped sinusoidal wave trains in response to each of said pulses, meansfor amplifying said damped wave trains, means for integrating saidamplified damped Wave trains over a period long as compared to the timebetween said horizontal synchronizing pulses and much shorter than theperiod of said vertical synchronizing pulses to provide triggeringpulses recurring at the rate of said vertical synchronizing pulses, andmeans for controlling said vertical scanning generator in accordancewith said triggering pulses.

11. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronzing signals includingvertical and horizontal synchronizing pulses, a resonant circuit tunedto a frequency substantially above the frequency of said horizontalsynchronizing pulses, means for coupling said television synchronizingsignals into said resonant circuit to produce damped sinusoidal Wavetrains in response to each of said pulses, means for integrating saiddamped Wave trains to provide triggering pulses recurring at the rate ofsaid vertical synchronizing pulses, and means for controlling saidvertical scanning generator in accordance with said triggering pulses.

12. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includingvertical and horizontal synchronzing pulses, a resonant circuit tuned toa frequency substantially higher than the frequency of said horizontalsynchronizing pulses, means for injecting said television synchronzingsignals into said resonant circuit to excite the same at its naturalfrequency, means for deriving from said resonant circuit dampedsinusoidal wave trains in response to each of said pulses, means forintegrating said damped Wave trains to provide triggering pulses havinga recurrence rate equal to that of said vertical synchronizing pulses,and means for controlling said vertical scanning generator in accordancewith said triggering pulses.

13. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includingvertical and horizontal synchronizing pulses, a resonant circuit tunedto a frequency substantially higher than the frequency of saidhorizontal synchronizing pulses, means utilizing said televisionsynchronizing signals for shock exciting said resonant circuit intooscillation at its natural frequency thereby to produce dampedsinusoidal wave trains in response to each of said pulses, means forintegrating said damped Wave trains to provide triggering pulses havinga recurrence rate equal to that of said vertical synchronizing pulses,and means for controlling said vertical scanning generator in accordancewith said triggering pulses.

14. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includingvertical and horizontal synchronizing pulses, a resonant circuit tunedto a frequency substantially higher than the frequency of saidhorizontal synchronizing pulses,.. an .ampiiflertuba .means `connect-'13 ing said resonant circuit betweena controlv elec,- trode and thecathode of said tube, means` including a condenser connected to. saidcontrol electrode for injecting said televisionsynchronizing signalsinto said resonant circuit to produce damped sinusoidal wave trainsthereaeross in response to each of said pulses, means for deriving froman output electrode of saidtubev said damped wave trains in ampliedform, means for integrating said damped wavetrains over a period long ascompared tothe time between said horizontal synchronizing pulses andmuch shorter than the period of said vertical synchronizing pulses toprovide triggering pulses recurring at the rate of said verticalsynchronizing pulses, and means for controlling said vertical scanninggenerator in accordance with said triggering pulses.

l5. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includingverticaland horizontal synchronizing pulses, a resonant circuit tuned toa frequency substantially higher than the frequency of said horizontalsynchronizing pulses, a pentode type amplifier tube, means connectingsaid resonant circuit between a control electrode and the cathode ofsaid tube, means including a condenser connected to said controlelectrode for injecting said television synchronizing signals into saidresonant circuit to produce damped sinusoidal Wave trains' thereacrossin response to each of said pulses, means for deriving from the screenelectrode of said tube said damped Wave trains in amplified form, meansfor integrating said damped wave trains to provide triggering pulsesrecurring at the rate or" said vertical synchronizing pulses, and meansfor controlling said vertical scanning generator in accordance with saidtriggering pulses.

16. In a television receiver, the combination of, a vertical scanninggenerator, a source of synchronizing signals including horizontal andvertical synchronizing pulses, a resonant circuit having a frequencysubstantially higher than the frequency of said horizontal synchronizingpulses, means for injecting said synchronizing signals into saidresonant circuit thereby to produce damped sinusoidal wave trains inresponse to each or" said pulses, an electronic switching circuit, meansfor keyingl saidl switching circuit to a given position in response tosaid damped wave trains, a horizontal scanning generator, means forderiving from said horizontal scanning generator control pulses having arecurrence rate equal to that of saidhorizontal synchronizing pulses,means for keyingsaid. switching circuit to the opposite position inresponse tosaid control pulses, means for integrating the output of saidswitching circuit to provide triggering pulses having a recurrence rateequal to that of said vertical synchronizing pulses, and means forcontrolling said vertical scanning generator in accoi-dance with saidtriggering pulses.

17. In a television receiver, the combination of, a vertical scanninggenerator, a source of synchronizing signals including horizontal andvertical synchronizing pulses, a resonant circuit tuned to a frequencysubstantially higher than the frequency of said horizontal synchronizingpulses, an amplifier tube, means connecting said resonant circuitbetween the controi electrode and the cathode of said tube, meansincluding a condenser connected to said control electrode for injectingsaid television synchronizing signals into acca-,aio

tical synchronizing said resonant circuit. to produce damped sinusoidalWave trains thereaCrQSs. IITQSDOnSe. t0 each of said pulses, meansfiorderiving from an output electrode. of said tube said dampedv wave trainsin ampliiiedform, an electronic switching circuit, means for keyingvsaid switching circuit. to a given position in, response tol saidamplified damped wave trains, aY horizontal scanning generatoreiectively; controlled by said horizontal synchronizing pulses, means.for deriving control pulses from said horizontal generator, means: forkeying said switching circuit to.V the` opposite po.- sition in responseto said control pulses, means for integrating theA output off saidswitching cir-v cuit over a period long as compared tothe time betweensaid horizontal synchronizing pulses and shorter than the periodv ofsaid vertical synchronizing pulses to obtain triggering pulses having arecurrencerate. equal! tothat of4 said vertical synchronizing pulses,and: means for controlling said vertical scanning generator inaccordance with said triggering pulses.

18. In a television receiver, vthe. combination of, avertical scanninggenerator, asource-of synchronizing signals including horizontal andvertical synchronizing pulses, a horizontalscanning generator, automaticfrequencyr control means control-led by said source for controlling thevfrequency of said horizontal scanning generator, and means controlledjointly by said source and saidY horizontal scanning generator forcontrolling the frequency oi said vertical scanning generator.

19. In a television receiver, the combination of, a vertical scanninggenerator, a source of syn-- chronizing signals including horizontalland vertical synchronizing pulses, a horizontal scanning generator,automatic frequency control means controlled by said source forcontrolling the frequency of said horizontal scanning generator,y andmeans controlled at least partially by said horijzontal scanninggenerator for` controlling the frequency of said vertical scanninggenerator.

20. l'n a television receiver, the combination of, aiirst scanninggenerator,t a source. o f synchronizing signals including horizontal andvertical synchronizing pulses, a second scanning generator, automaticfrequency Control` means con.- trolled by said source for controllingthe frequency of said second genera-tor, and means c on.- trolled atleastl in part by said' second scanning generator for controllingV the'frequency of said iirst scanning generator. V

21. In a television receiver, the combination of, aV rst scanninggenerator, a source of synchronizing signals includinghorizontal andverpulses, a, second scanning generator arranged to providek a.scanning` Wave of substantially different frequency than said rstscanning generator, automatic frequency control means controlled by saidsource for controlling the frequency of said second generator, and meanscontrolled at least in part by said second scanning generator forcontrolling the frequency of said first scanning generator.

22. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includinghorizontal and vertical synchronizing pulses, a horizontal scanninggenerator, automatic frequency control means controlled by saidhorizontal synchronizing pulses for stabilizing the frequency of saidhorizontal scanning generator and holding said generator in synchronismwith said horizontal synchronizing pulses, and means controlled at leastin part by said horizontal scanning genl erator for controlling thefrequency of said vertical scanning generator.

23. In a television receiver, the combination of, a vertical scanninggenerator, a source of syn-- chronizing signals including horizontal andvertical synchronizing pulses, a horizontal scanning generator, meansfor comparing the output of said horizontal scanning generator and saidhorizontal synchronizing pulses to derive a substantially unidirectionalvoltage representative of the phase relationship between said horizontalsynchronizing pulses and said horizontal scanning generator, means forcontrolling the frequency of said horizontal scanning generator inaccordance with said unidirectional voltage, and means including anelectronic switching circuit controlled jointly by said horizontalscanning generator and Vertical synchronizing pulses from said sourcefor controlling thefrequency of said vertical scanning generator.

24. In a television receiver, the combination of a vertical scanninggenerator, a source of synchronizing signals including horizontal andverticalsynchronizing pulses, a horizontal scanning generator, means forsynchronizing said horizontal scanning generator with said horizontalsynchronizing pulses, and means controlled at least in part by saidhorizontal scanning generator for synchronizing said vertical scanninggenerator with said vertical synchronizing pulses.

25. In a television receiver, the combination of, a vertical scanninggenerator, a source of television synchronizing signals includinghorizontal and vertical synchronizing pulses, means including a resonantcircuit for deriving from said source a periodic wave train havingamplitude variations corresponding to said vertical and horizontalsynchronizing pulses, means for integrating said periodic wave train toprovide triggering pulses having a recurrence rate equal to that of saidvertical synchronizing pulses, and means for controlling said verticalscanning generator in accordance with said triggering pulses.

26. In a television receiver, the combination of, a vertical scanninggenerator, a source of synchronizing signals including horizontal andvertical synchronizing pulses, a resonant circuit having a frequencyhigher than the frequency of said horizontal synchronizing pulses, meansfor injecting said synchronizing signals into said resonant circuit toproduce oscillations thereacross in response to each of said pulses, ahorizontal scanning generator effectively controlled by said horizontalsynchronizing pulses, and means controlled jointly by said producedoscillations and the output of said horizontal scanning generator forcontrolling said vertical scanning generator.

27. In a television receiver, the combination of, a vertical scanninggenerator', a source of syn-x chronizing signals including horizontaland vertical synchronizing pulses. a resonant circuit having a'frequencyhigher than the frequency of said horizontal synchronizing pulses, meansfor injecting said synchronizing signals into said resonant circuit toproduce oscillations thereacross in response to each of said pulses, ahorizontal scanning generator, means controlled jointly by saidhorizontal synchronizing pulses and the output of said horizontalscanning generator for controlling the frequency of said horizontalscanning generator, and means controlled jointly by said producedoscillations and the output of said horizontal scanning generator forcontrolling the frequency of said vertical scanning generator.

28. In a television receiver, the combination of, a vertical scanninggenerator, a source of synchronizing signals including horizontal andvertical synchronizing pulses, a narrow band resonant circuit having afrequency higher than the frequency of said horizontal synchronizingpulses, means for injecting said synchronizing signals into saidresonant circuit to produce oscillations thereacross in response to eachof said pulses, a, horizontal scanning generator, means for comparingthe output of said horizontal oscillator and said horizontalsynchronizing pulses to derive a substantially unidirectional voltagerepresentative of the phase relationship between said horizontalsynchronizing pulses and the output of said horizontal scanninggenerator, means for controlling the frequency of said horizontalscanning generator in accordance with said unidirectional voltage, meansfor deriving control pulses from said horizontal scanning generator,means jointly responsive to said control pulses and said producedoscillations for developing an artificial synchronizing signal havingportions corresponding to said horizontal synchronizing pulses andportions corresponding to said vertical synchronizing pulses, means forintegrating said artificial synchronizing signal to obtain triggeringpulses, and means for controlling said vertical scannng generator inaccordance with Said triggering pulses.

KURT ENSLEIN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,344,810 Fredendall Mar. 21, 1944 2,431,577 Moore Nov. 25,1947 2,458,156 Fredendall Jan. 4, 1949 2,529,172 Moe Nov. 7, 19502,611,033 Jones Sept. 16, 1952

